Although cellular network coverage in urban areas is often strong, there are many situations in which cellular coverage falls short of being able to provide the desired services. Some examples of these shortcomings are: lack of in-building coverage, masking in urban canyons, rural areas without coverage, geographic topology that impedes coverage, disaster situations where cellular infrastructure is destroyed, and so forth. Present day cellular networks require a connection to a base station in order to receive cellular service. That is because LTE and other cellular protocols are asymmetric and require a base station to be in the communication path.
In current wireless communication networks, the roles of the user equipment and the base stations are distinct. User equipment is a device through which a telephone call, an internet connection, or a GPS navigation session can transpire. Each of these functions is enabled by a connection to larger network—a cellular network, a Wi-Fi network, or a satellite network. Base stations can be stationary or mobile. But either way, when a smart phone is out of range of a base station, it is usually unable to make a voice call because it does not have connectivity to the core network.
Some mobile communication networks, however, do not require connectivity to the core network. For example, wireless device-to-device networks provide communication services to local users. One example is a push-to-talk network where users who are within range of one another can communicate over shared radio channels. Public safety personnel employ this type of technology in their land-mobile radios. Another example could be dual-use phones that can be cellular telephones when there is network connectivity and peer-to-peer telephones when there is no network connectivity. These phones could, for example, provide peer-to-peer connectivity over a Wi-Fi or Bluetooth network.
While land-mobile radios and dual-use phones can facilitate voice communication in the absence of a connection to a base station, and by extension, to the core network, these devices are not without their limitations. Land-mobile radios are not cellular telephones, which means that users desiring this type of connectivity must carry two separate devices. Land-mobile radio (“LMR”) users share the same channel. All users within the same LMR cell can, therefore, hear all communications. Devices that move outside of the range of the LMR network become unreachable.
Dual-use handsets are limited by the range of the base station or access point providing connectivity to the core network. Macro base stations typically have 15 km or more range. In contrast, the range of a Wi-Fi or Bluetooth connection is typically about 300 feet. There is accordingly a need for providing cellular network connectivity in the absence of a strong signal from a base station.